1. Field of the Invention
The present invention relates generally to a medical instrument for use in performing extracapsular cataract surgery, and a method for utilizing the medical instrument in performing such surgery.
More particularly, the invention relates to a medical instrument for use in performing an arterior capsulotomy during extracapsular cataract surgery. The medical instrument in accordance with the invention includes a wire cautery portion having a substantially circular shape which is connected with an electrical power source so as to heat the cautery portion to a burning temperature. In performing a capsulotomy during extracapsular cataract surgery, the cautery portion is positioned in contact with the anterior lens capsule so as to burn a circle therein to thus permit removal of a circular portion of the anterior lens capsule.
2. Description of Relevant Art
The human eye includes a lens having the configuration of a biconvex disc. The lens surface comprises a capsule which includes an anterior capsule and a posterior capsule which meet at an equator. Zonules extending from the ciliary body are attached to the lens equator so as to secure the lens in position. Disposed within the lens capsule is a softer cortex and a firm inner nucleus.
In a healthy human eye, the lens is formed of a clear crystalline protein, however, the lens will at times opacify to form what is known as a cataract. When it is required to remove the cataract, the surgical procedure generally employed heretofore by operating surgeons is known as in intracapsular cataract extraction. Such procedure entails making a 180.degree. incision at the superior limbus of the eye, retracting the iris, contacting the superior anterior lens capsule with an iceball (a cryoprobe), and extracting the entire lens within its capsule while separating same from the surrounding zonules.
In recent times, with the advent of the intraocular lenses, the surgical microscope and phacoemulsification, many eye surgeons have come to prefer a surgical procedure known as extracapsular cataract extraction. In such procedure, the eye is opened at the superior limbus, and either hooks, scissors or special forceps are employed to open the anterior lens capsule and express from within the capsule the nucleus of the lens. Thereafter, the remaining cortical material is removed so as to thus leave a clear posterior lens capsule in the eye, which capsule provides a barrier between the anterior chamber and the vitreous cavity of the eye.
Many factors are involved in attempting to successfully perform the extracapsular surgical method. One such factor resides in successful removal of a large portion of the anterior lens capsule, i.e., a capsulatomy, which facilitates access to the lens nucleus and removal of the cortical material. A hazard associated with such a capsulotomy is any contact between the anterior and posterior lens capsules, which results in adherence together of the anterior and posterior capsules and opacification of the posterior capsule. Accordingly, and because the lens capsule is highly elastic and the edges thereof roll and curl after the capsule has been cut, successful performance of a perfect capsulotomy is difficult.
Various methods have heretofore been employed for performing a capsulotomy during extracapsular cataract surgery. In one such method which has been commonly employed, a hooked needle (cystotome) is introduced into the eye at the limbus, and a 360.degree. incision is made at the periphery of the anterior capsule. In other known methods, the capsulotomy is performed with instruments such as scissors or special forceps. However, such known methods have attendant disadvantages due to the difficulties encountered in attempting to manipulate the aforesaid instruments within the very limited confines of the anterior chamber of the eye. Accordingly, there has developed a desideratum for a surgical instrument and technique for performing an anterior capsulotomy during extracapsular cataract surgery which overcomes the shortcomings and disadvantages attendant known instruments and techniques.
The present invention effectively overcomes the various disadvantages associated with known anterior capsulotomy instruments and techniques by providing a medical instrument including a cautery portion which is heated by an electrical current to a burning temperature so as to burn a very vlean and uniform circle in the anterior lens capsule. The resultant effect is similar to that of a branding iron, and permits ready removal of the portion of the anterior lens capsule within the burned circle to complete the capsulotomy and permit the remainder of the extracapsular surgical method to be performed.
Some of the various attempts which have been made in the general field of cautery-type or heated-type medical instruments include: the "Dental Instrument" disclosed in U.S. Pat. No. 1,335,987 issued in 1920 to Reid et al; the "Therapeutic Appliance" disclosed in U.S. Pat. No. 1,615,828 issued in 1927 to Chesney; the "Means for Effecting the Bloodless Removal of Diseased Tissue" disclosed in U.S. Pat. No. 1,919,543 issued in 1933 to Doane; and the "Device for Removing Excrescences and Polyps" disclosed in U.S. Pat. No. 4,202,338 issued in 1980 to Bitrolf. However, none of such known medical instruments are structurally or functionally suitable for use in eye surgery, and particularly for an anterior capsulotomy to be performed during extracapsular cataract surgery.